The overall goal of this project is to determine if - and if so, how - the metabolism of functionally important neuronal proteins is regulated by neuronal activity. The plan has been to identify a specific, easily studied, set of such proteins, to work out their metabolism in detail, and finally to determine whether alterations of synaptic input, secretion, or firing frequency alter any of the steps of the metabolic sequence. During the past three years, studies were completed on the distribution, structure, and detailed somatic metabolism of a realated group of peptides synthesized by certain identified neurons of the mollusc, Aplysia. The goals for the next three years are: 1) To characterize the axonal transport and axonal metabolism of these species. 2) Since they are thought to be secretory, to develop a preparation in which secretion can be tested and studied. This would then allow us to study the complete metabolic sequence of these peptides from synthesis through release. 3) To then use this preparation for the detailed regulatory studies described above.